If anything, what he failed at was doing a teardown rebuild after they couldn't follow up on the SB win with a playoff team. The writing was on the wall then, it wasn't just Manning and Ware who were over the hill. While there would have been a lot of complaints from the fan base, Elway and the franchise had built up enough goodwill to get away with one bad season and a lot of trades for futures. Instead he tried to do this rolling renewal which is what Pat Bowlen would have wanted and the fan base expects. They don't believe in bad seasons and when they happen they want to fire everyone in sight and act like it couldn't happen to this franchise. As part of that renewal were bad drafts, a poor coaching hire, and questionable contract decisions, especially the below average or worse QBs.
The last three draft classes have been pretty good value wise and the team stopped the bad habit of moving up in the draft and giving away too much capital for it because Russell, who is retiring, ran the draft for the most part. It led to much better results, as they stopped reaching for raw athletes and started valuing proven production more. The challenge for the next GM is 2-3 years down the road he will have to sign all these guys on rookie deals. The one decision of course everyone wants to talk about is Lock. The team almost has to stick with Lock one more season and then as he goes into his last year under rookie deal they can either extend him or draft a potential replacement. Unless a QB they really like falls to them at 9, they can't take the risk of giving away future year picks and then having another bad season because you are in the midst of trying to phase in a new QB. You do dumb things like that and you end up looking really stupid like the Texans do right now having traded away the #3 because they thought they were good.